JP2606312B2 - Ultrasonic motor - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an ultrasonic motor that generates a driving force by rotating a rotor by ultrasonic vibration.

(Prior Art) An ultrasonic motor having a structure in which a vertical-torsion composite piezoelectric vibrator is used as a stator and a rotor is pressed against an end face of the stator to rotate the rotor is proposed, for example, by Kumada, and is disclosed in Japanese Patent Application Laid-Open No. 61-1217.
No. 7 discloses this.

This motor is composed of a vertical-drawing composite piezoelectric vibrator in which a piezoelectric ceramic for longitudinal vibration excitation and a piezoelectric ceramic for torsional vibration excitation are overlapped and sandwiched and integrated with two cylindrical or cylindrical ultrasonic vibrators from both sides. An AC voltage is applied independently to the piezoelectric ceramic for longitudinal vibration excitation and the piezoelectric ceramic for torsional vibration excitation to induce an elliptical vibration on the end face of the stator. It gives a rotational movement.

(Problems to be Solved by the Invention) Generally, in order to realize a high-output and high-efficiency ultrasonic motor, it is necessary to increase both the vertical and horizontal amplitudes of the elliptical vibration generated on the end face of the stator as much as possible. .

By the way, since the sound speed of the shear wave is about 60% of the sound speed of the longitudinal wave, it is difficult to make the longitudinal vibration resonance frequency and the torsional vibration resonance frequency of the stator used in the ultrasonic motor of the above-mentioned conventional invention coincide. Therefore, when one vibration is driven by resonance, the other vibration is necessarily driven by non-resonance. It goes without saying that the vibration amplitude becomes extremely small as compared with the non-resonant drive resonance drive. Therefore, the amplitude of the elliptical vibration induced in this case is extremely small in either the vertical direction or the horizontal direction, so that it is difficult to realize a high-output, high-efficiency ultrasonic motor.

Note that it is possible to cause longitudinal resonance and torsional resonance simultaneously, but in this case, since the resonance frequencies are different from each other, elliptic vibration is not induced and the rotor does not rotate.

(Means for Solving the Problems) It is an object of the present invention to provide a high-output, high-efficiency ultrasonic motor that rotates a rotor using torsional vibration resonance and longitudinal vibration resonance.

FIG. 1 shows an example of the basic configuration of the ultrasonic motor of the present invention. In the figure, reference numeral 1 denotes a piezoelectric ceramic for exciting longitudinal vibration, which is sandwiched between the columnar ultrasonic vibrators 2 and 3 and integrated with an adhesive or the like, and forms a piezoelectric longitudinal vibrator as a whole. 4 in the figure
Is a piezoelectric ceramic for torsional vibration excitation, which is sandwiched between the columnar ultrasonic vibrators 5 and 6 and integrated with an adhesive or the like to form a piezoelectric torsional vibrator as a whole. In the figure, reference numeral 7 denotes a rotor, which is pressed against the above-mentioned vertical vibrator and torsional vibrator. Here, the resonance frequency of the vertical vibrator and the resonance frequency of the torsional vibrator are configured to be equal.

In the ultrasonic motor having the above-described configuration, when the longitudinal oscillator and the torsional oscillator are simultaneously driven for resonance and a phase difference of 90 ° C. is applied, the rotor rotates and a rotational output is obtained.

(Operation) The ultrasonic motor of the present invention is driven by the following principle. When the torsional vibrator resonates, a reciprocating rotational displacement occurs on the vibrator end face. On the other hand, when the longitudinal vibrator resonates, the vibrator undergoes expansion and contraction displacement in the axial direction. If the timings of the forward rotation displacement and the axial extension displacement are matched, the rotor is strongly pressed against the end face of the torsional vibrator and performs a rotary motion by frictional force. When the backward rotation displacement occurs, the longitudinal vibrator contracts in the axial direction and generates displacement, so that the pressure contact force received by the rotor is reduced and the rotor does not rotate. The torsional vibration amplitude is as small as micron order, but several tens of kilohertz
When vibrated in z, the time-integrated amplitude is transmitted to the rotor, and the rotor rotates at high speed in one direction.

In the motor of the present invention, the efficiency of the motor can be improved by increasing the friction at the contact surface between the torsional vibrator and the rotor and reducing the friction at the contact surface between the longitudinal vibrator and the rotor.

As described above, a structural feature of the present invention is that an independent torsional vibrator and a longitudinal vibrator are used. Therefore, the resonance frequencies of the two vibrators can be matched, and as a result, a torsional displacement and a telescopic displacement with a large amplitude can be used, so that a high-output, high-efficiency ultrasonic motor can be realized.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 2 is a view showing an ultrasonic motor according to an embodiment of the present invention. In the figure, 1 is 20Φ in diameter and 4mm in thickness polarized in the thickness direction.
Is a piezoelectric ceramic for longitudinal vibration excitation. The support body 10 and the ultrasonic vibrators 2 and 3 sandwich the piezoelectric ceramic and are integrated using an adhesive. This becomes a longitudinal oscillator. In the figure, reference numeral 4 denotes a torsional excitation piezoelectric ceramic having a diameter of 20Φ and a thickness of 4 mm, which is polarized in the circumferential direction. As in the case of the vertical vibrator, the ceramics, the ultrasonic vibrators 5 and 6, and the support 10 are integrated using an adhesive to form a torsional vibrator. A shaft 8 is screwed into the center of the end face of the torsional vibrator. Then, the rotor 7 is pressed between the longitudinal vibrator and the torsional vibrator via the bearing 9. The total length of the vertical vibrator was 68 mm, the total length of the torsional vibrator was 43 mm, and the thickness of the rotor was 10 mm.

The rotor was rotated when an alternating voltage of 25 kHz and 200 V was applied independently to the piezoelectric ceramic for longitudinal vibration excitation and the piezoelectric ceramic for torsional vibration excitation, and the phase difference was 90 ° C. Its rotation speed was 130 rpm and the starting torque was 7 kgf · cm.

(Effects of the Invention) As is apparent from the above embodiment, the motor of the present invention drives the piezoelectric longitudinal vibrator and the piezoelectric torsional vibrator by resonating, so that an ultrasonic motor having a small diameter and generating a large torque can be obtained. .

[Brief description of the drawings]

FIG. 1 is a diagram showing the principle of operation of the present invention, and FIG. 2 is a diagram showing an embodiment of the present invention. 1 in the figure: piezoelectric ceramics for longitudinal vibration excitation, 4 ... piezoelectric ceramics for torsional vibration excitation, 2, 3, 5, 6 ... ultrasonic vibrator, 7 ... rotor, 8 ...
Shaft, 9... Bearing, 10...

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Takeshi Inoue 5-33-1, Shiba, Minato-ku, Tokyo NEC Corporation (72) Inventor Tadasuho Uchikawa 5-33-1, Shiba, Minato-ku, Tokyo NEC (56) References JP-A-62-247769 (JP, A) JP-A-63-114576 (JP, A)

Claims (1)

(57) [Claims] 1. An ultrasonic motor comprising a rotor sandwiched between a piezoelectric longitudinal vibrator and a piezoelectric torsional vibrator and pressed into contact therewith.